/*
 * SocketConnection.java   0.0.1    28/set/2009
 * 
 * Copyright (c) 2009 mentalsmash.org
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * The use of the Apache License does not indicate that this project is
 * affiliated with the Apache Software Foundation.
 */ 
package org.mentalsmash.tazio.net.cs.client;

import java.io.IOException;
import java.io.Serializable;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.mentalsmash.tazio.net.cs.MessageInputStream;
import org.mentalsmash.tazio.net.cs.MessageOutputStream;
import org.mentalsmash.tazio.net.cs.RuntimeCSSubsystemException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Implementation of {@link Connection} using Internet sockets
 * to communicate with the server.
 * <p>
 * This implementations uses an {@link ExecutorService} instance
 * passed to it at construction time, to send a request to the 
 * server and receive a response. Therefore - depending of the kind of
 * <tt>Executor</tt> passed at construction time - there may be a single thread
 * sending each message through this connection (and possibly other connections), or 
 * at the opposite extreme, a thread may be created on a per-request basis.
 * </p>
 * <p>
 *   <strong>Therefore</strong>, do not make any assumptions on how the requests are
 *   executed, except that they are not made by the calling thread
 * </p>
 * @author Andrea Reale <andrea.reale@gmail.com>
 * @version 0.0.1
 */
public class SocketConnection implements Connection {

    private final static Logger log = LoggerFactory.getLogger(SocketConnection.class);

    private final ExecutorService executor; //the executor that will send the requests to the server
    private final Socket connectedSocket; //the socket used for communications with the server
    private SocketRemoteServer server; //the server referenced by this connection

    /*
     * Streams used to read and write from the socket
     */
    private final MessageOutputStream outputStream;
    private final MessageInputStream inputStream;
    
    /**
     * This lock is used to allow multiple threads to write and recevie messages from this
     * connection. But none can close the socket while someone is reading.
     */
    //TODO: Double check wheter this is the right behaviour or not
    private final ReadWriteLock doNotCloseMeLock = new ReentrantReadWriteLock(true);

    /**
     * Creates a <tt>SocketConnection</tt>.
     * <p>
     * This <tt>Connection</tt> will be bound to the address specified by the passed
     * {@link SocketRemoteServer} parameter 
     * </p>
     * <p>
     * The created <tt>Connection</tt> will send requests and receive responses by submitting
     * those operations to the <code>executor</code> passed as argument.
     * </p>
     * @param executor the {@link ExecutorService} that will execute the actual communication procedure
     * @param server a reference to the remote server this connection will be associated to
     * @throws IOException If an I/O error occurs.
     */
    protected SocketConnection(ExecutorService executor, SocketRemoteServer server) throws IOException{
	if(executor == null || server == null) {
	    log.error("Passed a null executor or server");
	    throw new IllegalArgumentException("Neither executor or server can be null");
	}

	this.executor = executor;
	this.server = server;

	InetSocketAddress socketAddr = server.getSocketAddress();
	connectedSocket = new Socket(socketAddr.getAddress(), socketAddr.getPort());

	outputStream = new MessageOutputStream(connectedSocket.getOutputStream());
	inputStream = new MessageInputStream(connectedSocket.getInputStream());

    }

    /* (non-Javadoc)
     * @see org.mentalsmash.tazio.net.cs.client.Connection#getRemoteServer()
     */
    @Override
    public RemoteServer getRemoteServer() {
	doNotCloseMeLock.readLock().lock();
	try{
	    return this.server;
	} finally {
	    doNotCloseMeLock.readLock().unlock();
	}
    }



    /* (non-Javadoc)
     * @see org.mentalsmash.tazio.net.cs.client.Connection#isValid()
     */
    @Override
    public boolean isValid() {
	doNotCloseMeLock.readLock().lock();
	try {
	    return server != null && connectedSocket.isConnected();
	} finally {
	    doNotCloseMeLock.readLock().unlock();
	}
    }

    /* (non-Javadoc)
     * @see org.mentalsmash.tazio.net.cs.client.Connection#sendRequest(java.io.Serializable)
     */
    @Override
    public Serializable sendRequest(Serializable request) throws IOException,
    ConnectionStateExeption {

	Serializable response = null;

	doNotCloseMeLock.readLock().lock();
	try {
	    if(!isValid()) {
		String  msg = "Invalid connection. Is the RemoteServer connected?";
		log.error(msg);
		throw new ConnectionStateExeption(msg); 
	    }

	    outputStream.writeMessage(request);
	    response = inputStream.readMessage();
	} catch(ClassNotFoundException e) {
	    String msg = "Can't rebuild message object. Class not found";
	    log.error(msg,e);
	    throw new RuntimeCSSubsystemException(msg,e);
	} finally {
	    doNotCloseMeLock.readLock().unlock();
	}

	return response;
    }

    /* (non-Javadoc)
     * @see org.mentalsmash.tazio.net.cs.client.Connection#sendRequestAsync(java.io.Serializable)
     */
    @Override
    public Future<Serializable> sendRequestAsync(final Serializable request)
    throws ConnectionStateExeption {

	Future<Serializable> response;

	doNotCloseMeLock.readLock().lock();
	try {
	    if(!isValid()) {
		String  msg = "Invalid connection. Is the RemoteServer connected?";
		log.error(msg);
		throw new ConnectionStateExeption(msg); 
	    }

	    response = executor.submit(new Callable<Serializable>() {
		@Override
		public Serializable call() throws Exception {
		    Serializable response = null;
		    outputStream.writeMessage(request);
		    try {
			response = inputStream.readMessage();
		    } catch (ClassNotFoundException e){
			String msg = "Can't rebuild message object. Class not found";
			log.error(msg,e);
			throw new RuntimeCSSubsystemException(msg,e);
		    }
		    
		    return response;
		}
	    });
	} finally {
	    doNotCloseMeLock.readLock().unlock();
	}

	return response;
    }

    @Override
    public Future<RequestStatus> sendMessageAsync(final Serializable message) throws ConnectionStateExeption {
	Future<RequestStatus> toReturn;

	doNotCloseMeLock.readLock().lock();

	try {
	    if(!isValid()) {
		String  msg = "Invalid connection. Is the RemoteServer connected?";
		log.error(msg);
		throw new ConnectionStateExeption(msg); 
	    }

	    toReturn = executor.submit(new Callable<RequestStatus>() {
		public RequestStatus call() throws Exception {
		    RequestStatus toReturn = null;
		    try {
			outputStream.writeMessage(message);
		    } catch (Exception e) {
			toReturn = RequestStatus.EXCEPTION_OCCURRED; //nice but useless
			throw e;
		    }

		    toReturn = RequestStatus.OK;

		    return toReturn;
		}
	    });
	} finally {
	    doNotCloseMeLock.readLock().unlock();
	}

	return toReturn;

    }

    @Override
    public void sendMessage(Serializable message) throws IOException,
    ConnectionStateExeption {

	doNotCloseMeLock.readLock().lock();

	try {
	    if(!isValid()) {
		String  msg = "Invalid connection. Is the RemoteServer connected?";
		log.error(msg);
		throw new ConnectionStateExeption(msg); 
	    }
	    outputStream.writeMessage(message);
	} finally {
	    doNotCloseMeLock.readLock().unlock();
	}


    }

    /* (non-Javadoc)
     * @see org.mentalsmash.tazio.net.cs.client.Connection#close()
     */
    @Override
    public void close() {
	log.debug("Waiting for other threads to release the connection");
	doNotCloseMeLock.writeLock().lock(); //X-clusive
	log.debug("Closing the connection");
	
	try {
	    this.server.setConnection(null);
	    this.server = null;
	    try {
		inputStream.close();
		outputStream.close();
		connectedSocket.close();
	    } catch (IOException e) {
		log.debug("Error while closing connection." ,e);
		//never mind, I'm closing...
	    }
	} finally {
	    doNotCloseMeLock.writeLock().unlock();
	}
	
    }





}


